During operation of road milling machines, in particular of the large-scale milling machine type, there is often a need to replace the milling unit composed of milling drum box and milling drum, for example, in order to enable different working widths. Such road milling machines are often used in road construction for the controlled removal of the cover layer of asphalt roads. Essential elements of such a road milling machine are a machine part comprising a machine frame, an operator platform, a drive engine as well as travelling devices such as wheels and/or crawler tracks, which are driven by the drive engine. The travelling devices are usually connected to the machine frame via height-adjustable lifting columns, so that the distance of the machine frame to the ground is adjustable in the vertical direction by adjustment of the lifting columns. Furthermore, the road milling machine comprises, as the milling part, the milling unit comprising the milling drum for milling ground material and the milling drum box for covering the milling drum to the sides and to the top. Usually, the milling drum comprises a hollow-cylindrical support tube as well as a plurality of milling tools on the outer jacket surface of the support tube. The milling unit can be detachably fastened via a fastening device which retains the milling unit to the road milling machine. Such a road milling machine is known from DE 10 2011 018 222 A1, for example.
Often times, the machine per se and the milling unit (hereinafter, this includes variants with and without a milling drum arranged inside the milling unit) are transported separately in order to not have to use heavy duty vehicles due to the existing legal restrictions with respect to maximum transport dimensions and maximum transport weight. It will be appreciated that working times as short as possible are desired for dismounting and mounting the milling unit from/to the machine part. Moreover, there is often a need to be able to mill different milling widths with one and the same road milling machine. In this regard, it is preferred when different milling units can be mounted in an alternating manner and rapidly replaced on one and the same road milling machine. Often times, the milling unit is detachably connected to the machine part via massive fastening screws and corresponding locking nuts or also via other types of detachable fastening devices.
The most time-consuming step of the dismounting and mounting process often consists in the positioning of the milling unit relative to the road milling machine. Related special-purpose vehicles which are self-propelled, self-steered and height-adjustable, for example, often need to be transported separately and are very expensive. Moreover, there is only limited space available, in particular in road construction sites, so that space-consuming maneuvering is not possible.